This was done on a team bike but it was done on the diffuse, i have tried doing it on the specular but it never shows up so your best bet is playing around with it on the diffuse on a white logo or something.

Attempted Photographer < I try.... Shitty racer, Only good at screenshots, forever pretending to be quick at MXS.

It's not too hard to do, but this is an example off of 6D's SX skins of what you need to do to get it to work.Diffuse: it is set to a low opacity so it is only just noticable over the top of a white logo.

Spec: I beleive this was set to like 3 or 4 percent opacity, which makes it barely noticable however in game it looks really nice when in the light.